Degradation of immunoglobulins, protease inhibitors, and interleukin-1 by a secretory proteinase of Acanthamoeba castellanii

The effect of a secretory proteinase from the pathogenic amoebae Acanthamoeba castellanii on hosts defense-oriented or regulatory proteins such as immunoglobulins, interleukin-1, and protease inhibitors was investigated. The enzyme was found to degrade secretory immunoglobulin A (sIgA), IgG, and IgM. It also degraded interleukin-1alpha (IL-1alpha) and IL-1beta. Its activity was not inhibited by endogenous protease inhibitors, such as alpha2-macroglobulin, alpha1-trypsin inhibitor, and alpha2-antiplasmin. Furthermore, the enzyme rapidly degraded those endogenous protease inhibitors as well. The degradation of hosts defense-oriented or regulatory proteins by the Acanthamoeba proteinase suggested that the enzyme might be an important virulence factor in the pathogenesis of Acanthamoeba infection.